Nerol oxide is a valuable base material in perfumery and occur naturally as an ingredient of Bulgarian rose oil (0.038%) and grape juice. It exists naturally as a racemic mixture of (R and S) isomers of 3,6-dihydro-4-methyl-2-(2-methyl-1-propenyl)-2H pyran. The olfactory properties of racemic nerol oxide are comparable to those of diastereoisomeric rose oxides as regards totality and strength and is dominated by a powerful greenish-spicy note of the geranium type corresponding to the odour of (−)-cis-rose oxide.
Nerol and geraniol are the monoterpenic constituents of Cymbopogon spp. (lemon grass) These are the geometrical (cis and trans) isomers and can also be easily obtained by chemical reduction or catalytic hydrogenation of citral, another very common monoterpenic constituent of lemon grass.
Ohloff prepared the intermediate 3,7-dimethyl-octa-2,5-dien-1,7-diol from nerol by its photosensitized air oxidation followed by reduction and cyclisation with an acid to obtain racemic nerol oxide [G. Ohloff, K. H. Schulte-Elite & B. Willhalm Helv. Chim. Acta. 47, 602, 1964]. In another publication nerol was first subjected to epoxidation at C6–C7 double bond and the epoxy derivative so obtained was heated in dimethyl amine at 150° to give 3,7-dimethyl-6-dimethyl amino-2-octen-1,7-diol which on oxidation with hydrogen peroxide and pyrolysis at 180° C. gave a diol intermediate that on acid catalysed cyclisation led to the formation of nerol oxide [G. Ohloff & B. Lienhard Helv. Chim. Acta. 48, 182, 1965].
Tyman and Willis reported the total synthesis of nerol oxide by reaction of 3-methyl-2-butenal and 3-methyl-3-butenol in presence of an acid. [J. H. P. Tyman & B. J. Willis Tet. Lett. 4507, 1970]. Hasegawa T. Co Ltd. Japan in 1980 disclosed that 3,7-diethyl-1-octen-3-ol-5-one on reduction with Lithium aluminium hydride (LAH) followed by its cyclisation producing nerol oxide [Hasegawa T. Co Ltd. Japan, Chem. Abstracts, 93, 239702, 1980].
In another publication Ohloff et al. in 1980 described the synthesis of optically active nerol oxide from (−)-(R)-linalool in a nine step reaction sequence which is more of academic interest [G. Obloff, W. Giersch, K. M. Schulte-Elite, P. Enggist & E. Demole Helv. Chim. Acta. 63, 1582, 1980]. Thus the methodologies or processes reported in prior art are generally are of academic interest, non-ecnomical as well as cumbersome. The overall yield of the final product nerol oxide is also low.